To set the tempo for you entire score, choose Score from the Display menu and set the tempo to the value you want.
To make a tempo change at the current time, click on the tempo button in the main control area and set a new tempo.
To make a number of tempo changes (to accelerate or decelerate tempo gradually), use the Controller Editor. Select Tempo from the Data Type list box in the control area of the Controller Editor. Select the Pencil tool and click where you want to enter a single tempo change. You can also drag the mouse to enter a group of tempo change events. When you drag in tempo changes, the density of the events is controlled by the step setting in the Step list box.